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I need to switch three different supply and for that I am planning to use 3:1 Analog switch something as shown in the below Block diagram. enter image description here

As we know there will an on resistance(Ron) for these kind of switches. So will this resistance lower down the voltage once it is switched through the analog switches? My understanding was, since this resistance will come in the series of load resistance of IC, so should impact only the flow of current not the voltage.

Is my understanding is correct? If not, could some one please suggest an another way of switching the 3 power supply with two control inputs?

Thanks

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    \$\begingroup\$ Two SPDT relays. \$\endgroup\$ – Ignacio Vazquez-Abrams May 18 '18 at 11:31
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    \$\begingroup\$ Use latching relays if reduced power consumption is desired. Those you can 'power' only briefly and they'd latch in that position indefinitely. \$\endgroup\$ – Richard the Spacecat May 18 '18 at 11:42
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Your understanding is not correct. The on resistance of the switch will only drop zero voltage if you draw zero current through the switch. Ohm's law should tell you right away that the voltage drop across the switch is going to be a direct function of the switch resistance and how much current that you intend to pass through the switch.

I get the sneaking suspicion that you are making an X-Y type query here. You have three power supplies that you need to gate to a device under test. Why don't you consider making a single power supply that has an adjustable output. There are plenty of both power management ICs (both switching types and linear types of regulators) that support adjustment of the output voltage through a feedback voltage divider. These are very easy to setup with a switch IC like you showed in your question that selects one of three separate sets of feedback resistors to set the output voltage. These resistors are usually in the 100's or 1000's of ohm sizes operating at low current such that the low RdsON for a modern type of analogue switch part will be insignificant to the application.

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  • \$\begingroup\$ Your idea looks pretty good, however it will not suits my requirement. Since the same supply which is going to switch has been used for some other IC's as well \$\endgroup\$ – Sanjeev Kumar May 18 '18 at 14:45

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